1. Field of the Invention
The present invention relates to a pintle wire, particularly but not exclusively for use in joining the ends of industrial fabrics, such as papermachine clothing, for example press felts and dryer fabrics.
2. Description of the Related Art
It is known to join the ends of an industrial fabric using a monofilament pintle wire so as to provide an endless belt. Each end of the fabric is provided with outwardly extending loops, the two sets of loops being interdigitatable and capable of union by a pintle wire.
These known monofilament pintle wires have a low tensile strength. The wires may additionally have flaws in the monofilament structure. As a result the wires often break on insertion through the tunnel defined by the interdigitated loops. More importantly, the wires may break while the belt is in operation. This may lead to belt damage and necessitate the disposal of the belt before the end of its expected working life. As these belts, particularly those for use in papermaking, are extremely expensive this problem is of considerable importance.
Another problem with these known monofilament pintle wires is that the diameter of the wires are such that they do not fill the loop area and as such result in a high degree of localised permeability. This, once again, is of particular importance in the field of papermaking, where variations in permeability in the belt result in marking of the paper produced on the belt.
As an alternative to monofilament pintle wires multifilament pintle wires comprising polyamide have been used which are resin-treated. The resin treatment involves impregnation with phenolic or epoxy polymer resin which is then cured. Alternatively multifilament pintle wires have been used which comprise polyamide multifilaments wrapped around a polyamide monofilament core. Both of these known structures serve to give the polyamide multifilament a stiffness akin to a monofilament. Resin treatment processes are a burden in terms of increased material costs and production times, as well as being increasingly environmentally unsound due to the fact that treatment with these resins requires a considerable amount of organic solvent. Furthermore polyamides are generally lacking in abrasion resistance.
For dryer fabrics the aramid NOMEX (trade mark) and NOMEX (trade mark)/polyester blends have been used but neither can withstand the high loads present in the nips of a press section.